Slot array antenna



June 22, 1954 E. M. PURCELL 9 SLOT ARRAY ANTENNA Filed April 5-. 1946 INVENTOR EDWARD M PURCE LL ATTORNEY Patented June 22 1954 SLOT ARRAY ANTENNA Edward M. Purcell, Cambridge, Mass., by mesne assignments, to the United assignor, States of America as represented by the Secretary of the Navy Application April 3, 1946, Serial No. 659,185

11 Claims. 1

This invention relates to antennas and more specifically to an antenna formed by a zigzag slot in a rectangular wave guide.

An antenna formed by a linear array of dipoles placed end to end and excited in phase has good directivity in a plane passing through the length of the array. The object of this invention is to provide an antenna having the above mentioned characteristics and formed by a section of wave guide.

Another object is to by a slot through the gular waveguide.

The foregoing and other objects will be apparent from the following specifications when considered with the accompanying drawing, the single figure of which shows an embodiment of the invention.

Referring to the accompanying drawing, a section of rectangular wave guide I is shown. The narrow dimension of wave guide l0 decreases gradually over the length of the guide. Through the wall of one broad side of wave guide I 0 is a longitudinal zigzag slot II, that is, a zigzag slot symmetrically disposed about the longitudinal centerline of the broad face. The design consideration of slot H may be specified by the dimensions I 2, 13, I4 and E5. The dimension [2 is the interval between points at which the centerline of the slot crosses the longitudinal centerline of the broad face of waveguide 10. The dimension 13 is the width of the slot ll. Dimension I4 is the thickness of the wall of waveguide I 0 through which the slot H extends. The dimension is the angle between sections of slot II. The dimension I2 is substantially equal to one half wavelength of the electromagnetic energy in the wave guide. The dimension [4, the depth of the slot, is equal to substantially one quarter wavelength of the electromagnetic energy in free space. The dimensions l3, the width of the slot, and i5, the angle between sections of the slot, control the degree of coupling between slot 1 l and wave guide It.

In operation, electromagnetic energy is coupled at 9 to the section of wave guide I0 at the end having the largest narrow dimension. The section of wave guide It is terminated at the small end by a load (not shown) substantially matched to the wave guide It). The termination may be a short or open circuit if it is properly located in reference to the slot II. The electromagnetic energy will be radiated through the slot Ii, each straight section of the slot H acting as a half wave dipole. As the energy progresses provide an antenna formed wall of a section of rectanthrough the wave guide It from the source to the termination it will be progressively decreased by the amount radiated by each section of the slot II. To maintain uniform distribution of energy radiated along the length of the slot I l, the narrow dimension of wave guide II] is decreased as illustrated. Uniform distribution of radiated energy could also be obtained by gradual increase of the width of the slot l I, dimension l3, from the source to the termination.

Although there is shown and described herein a preferred embodiment of the present invention, numerous possible modifications will be readily apparent to those skilled in the art.

What is claimed is:

1. An antenna for radio frequency energy comprising, a section of waveguide having a slot in the wall thereof, said slot being in the form of a longitudinal zigzag.

2. An antenna for radio frequency energy comprising, a section of rectangular waveguide having a slot through one wall of the broad dimension, said slot being in the form of a longitudinal zigzag.

3. An antenna for radio frequency energy comprising, a section of rectangular wave guide having a slot formed in a broad wall thereof, said slot being in the form of a longitudinal zigzag, successive portions of said zigzag slot intersecting a plane through the longitudinal axis of said Wave guide at equally spaced points, said successive portions being operable as dipole radiators of said radio frequency energy.

4. Apparatus as in claim 3 wherein said wave guide has the narrow Wall thereof tapered, the degree of taper being such that radiation from said section is linear.

5. Apparatus as in claim 3 wherein said broad wall having said slot formed therein has a thickness substantially equal to a quarter Wave length of said radio frequency energy.

6. Apparatus as in claim 3 wherein the spacing between said points is substantially equal to a half wave length of said radio frequency energy.

7. An antenna array comprising a section of rectangular wave guide having broad and narrow walls, said wave guide having a longitudinal zigzag slot through one broad wall thereof.

8. An array comprising, a section of hollow rectangular Wave guide formed of conductive material, said wave guide having a zig-zag slot through one broad wall thereof disposed about the longitudinal center line of said one broad wall, the center line of said slot crossing said longitudinal center line at intervals equivalent to substantially a half wave length of the electromagnetic energy in the wave guide, and means for coupling energy to said wave guide.

9. An antenna array comprising a section of rectangular wave guide having broad and narrow walls, said narrow walls decreasing in dimension linearly with the-distance from one end to the other of said section, said wave guide having a plurality of overlapping apertures of rectangular cross section formed in one broad wall thereof, said apertures being disposed along the longitudinal axis of said one broad wall at an angle thereto to form a continuous zig-zag slot in said broad wall, and means for coupling energy to said one end of said Wave guide section.

10. An antenna array comprising a section of rectangular wave guide having broad and narrow walls, said narrow Walls decreasing in dimension linearly with the distance from one end to the other of said section, said wave guide having a plurality of apertures of elongated rectangular cross section formed about the longitudinal center line of one broad wall thereof, adjacent apertures being joined together at their ends and the center line of each aperture intersecting said longitudinal center line at an angle, the distance between adjacent intersections of aperture center lines with said longitudinal center line being substantially equal to a half-wave length of the electromagnetic energy in the wave guide, and means for coupling energy to said one end of said wave guide.

11. An antenna array comprising a section of rectangular wave guide having broad and narrow walls, one of said broad walls having a thickness substantially equal to a quarter wave length of the energy within said guide at the frequency of operation and said narrow walls decreasing in dimension linearly with the distance from one end to the other of said section, said one broad wall having a series of overlapping elongated apertures cut therethrough and forming a zigzag'slot disposed symmetrically about the longitudinal center line of said broad wall, and means for coupling energy to said one end of said wave guide.

References Cited in the file of this patent UNrrEUsTATEs PATENTS Number Name Date 2,235,162 Moser et al Mar. 18, 1941 2,238,770 Blumlein Apr. 15, 1941 2,402,622 Hansen June-25, 1946 2,405,242 Soutliworth Aug. 6, 1946 2,408,435 Mason Oct. 1, 1946 2,414,266 Lindenblad Jan. 14, 1947 2,479,209 Chu Aug. 16, 1949 2,482,162 Feldman Sept. 20, 1949 2,489,288 Hansen Nov. 29, 1949 "2,501,105 Steinberger Mar. 21, 1950 

